Any structure that is built adjacent to a body of water or surrounded by a body of water, is normally made accessible to boats, barges, and other marine vessels. However, when attempting to tie up a vessel to the stationary structure, care must be exercised particularly in the instance of heavier vessels to avoid damaging either the structure or the vessel.
For example, a vessel attempting to tie up to, or become docked to a structure in an open body of water, is subjected to prevailing atmospheric conditions. The latter can include both wind and tide forces which could affect the operation of the vessel.
Most notably, in a docking operation, the vessel's speed is substantially reduced to minimize its impact when and if it contacts the offshore structure. Usually, however, the vessel will make some contact with the fixed structure, the degree of its striking force being a function of the above noted natural conditions.
In view of the anticipated docking difficulties, virtually all offshore structures are furnished with a suitable mooring apparatus. To be effective, such an apparatus must be capable of absorbing the initial shock of a vessel coming into, or being pulled into contact with the structure. Such shock absorbing devices are of particular relevance in tidal waters where the direction of flow, and the velocity of the water about the stationary structure can be drastic.
In the instance of most offshore steel jacket type structures where large tankers or similar supply vessels will frequently dock, the structure is always provided with a shock absorbing apparatus. The latter normally embodies means whereby, should the floating vessel accidentally come into sharp or uncontrollable contact with the structure, the resulting shock will to a large part be absorbed or dampened rather than being transferred to the structure's support legs.
Such mooring facilities are normally at least partially submerged at the structure. When properly located, they balance the resisting force to overcome the vessel's momentum. Secondly the variation in the height of the tide may be such as to warrant that the shock absorbing device be relatively high to cover the types of vessels which are normally being brought in contact with it.
Among the many types of shock absorbing means used on both vessels and on platforms, there are both mechanical and non-mechanical types. In the instance of the simpler types, interconnected and operable parts are avoided due to the corrosive atmosphere and the periodic submersion in the water to which the mooring device will be subjected. In the instance of steel offshore structures, the effect of corrosive deterioration on the shock absorbing device will be noticeably pronounced.
On some of these devices the use of a compressible and reformable material to absorb a vessel's initial shock is widespread. Such materials include rubber, various plastics, and inflatable bodies.
Toward overcoming or at least alleviating the problem of the harsh environment to which the shock absorbing devices are subjected, the present invention provides in an offshore platform, mooring means capable of receiving and absorbing the impact of a vessel which is moved against it. The mooring means includes at least one shock absorbing member which is capable of deflecting in response to the initial force of the moving vessel.
Toward retaining a degree of viability in the shock absorbing system, even when it has become damaged or experiences excessive wear, a stabilizing means is provided which is provisionally incorporated into the shock absorbing cell. The stabilizer serves the purpose of minimizing displacing movement to which the latter will be subjected.
The stabilizer includes primarily a collar-like device which is adapted for detachable connection to the shock absorbing cell which is incorporated into the shock absorbing apparatus. The stabilizer in achieving its purpose, is removably connected to the shock absorbing cell. This is achieved in a manner to limit or minimize movement between the parts of said device which would otherwise be displaced in response to the contact between a floating vessel and the marine structure.
It is therefore an object of the invention to provide in an offshore marine platform of the type contemplated, means whereby a ship docking member might be protected from excessive wear under extenuating operating conditions.
A further object is to provide a shock absorbing member of the type contemplated to which a stabilizer is adapted for connection to preclude major damage after a shock absorbing cell has become substantially inoperative.
A still further object of the invention is to provide a ship docking system of the type contemplated in which the shock absorbing mooring arrangement can be stabilized or neutralized pending necessary repairs to the unit as the result of extreme displacing forces.